The present invention relates to methods and compositions for analyzing nucleic acids, and in particular, methods and compositions for detection and characterization of nucleic acid sequences and sequence changes.
The detection and characterization of specific nucleic acid sequences and sequence changes have been utilized to detect the presence of viral or bacterial nucleic acid sequences indicative of an infection, the presence of variants or alleles of mammalian genes associated with disease and cancers, and the identification of the source of nucleic acids found in forensic samples, as well as in paternity determinations. As nucleic acid sequence data for genes from humans and pathogenic organisms accumulates, the demand for fast, cost-effective, and easy-to-use tests for as yet unknown, as well as known, mutations within specific sequences is rapidly increasing.
A handful of methods have been devised to scan nucleic acid segments for mutations. One option is to determine the entire gene sequence of each test sample (e.g., a clinical sample suspected of containing bacterial strain). For sequences under approximately 600 nucleotides, this may be accomplished using amplified material (e.g., PCR reaction products). This avoids the time and expense associated with cloning the segment of interest. However, specialized equipment and highly trained personnel are required for DNA sequencing, and the method is too labor-intense and expensive to be practical and effective in the clinical setting.
In view of the difficulties associated with sequencing, a given segment of nucleic acid may be characterized on several other levels. At the lowest resolution, the size of the molecule can be determined by electrophoresis by comparison to a known standard run on the same gel. A more detailed picture of the molecule may be achieved by cleavage with combinations of restriction enzymes prior to electrophoresis, to allow construction of an ordered map. The presence of specific sequences within the fragment can be detected by hybridization of a labeled probe, or, as noted above, the precise nucleotide sequence can be determined by partial chemical degradation or by primer extension in the presence of chain-terminating nucleotide analogs.
For detection of single-base differences between like sequences (e.g., the wild type and a mutant form of a gene), the requirements of the analysis are often at the highest level of resolution. For cases in which the position of the nucleotide in question is known in advance, several methods have been developed for examining single base changes without direct sequencing. For example, if a mutation of interest happens to fall within a restriction recognition sequence, a change in the pattern of digestion can be used as a diagnostic tool (e.g., restriction fragment length polymorphism [RFLP] analysis). In this way, single point mutations can be detected by the creation or destruction of RFLPs.
Single-base mutations have also been identified by cleavage of RNA-RNA or RNA-DNA heteroduplexes using RNaseA (Myers et al., Science 230:1242 [1985] and Winter et al., Proc. Natl. Acad. Sci. USA 82:7575 [1985]). Mutations are detected and localized by the presence and size of the RNA fragments generated by cleavage at the mismatches. Single nucleotide mismatches in DNA heteroduplexes are also recognized and cleaved by some chemicals, providing an alternative strategy to detect single base substitutions, generically named the xe2x80x9cMismatch Chemical Cleavagexe2x80x9d (MCC) (Gogos et al, Nucl. Acids Res., 18:6807-6817 [1990]). However, this method requires the use of osmium tetroxide and piperidine, two highly noxious chemicals which are not suited for use in a clinical laboratory. Enzymes such as the bacteriophage T4 endonuclease VII have been used in xe2x80x9cEnzymatic Mismatch Cleavage: (EMC) (Youil, et al., Genomics, 32:431 [1996]). However, all of the mismatch cleavage methods lack sensitivity to some mismatch pairs, and all are prone to background cleavage at sites removed from the mismatch. Furthermore, the generation of purified fragments to be used in heteroduplex formation is both labor intensive and time consuming.
RFLP analysis suffers from low sensitivity and requires a large amount of sample. When RFLP analysis is used for the detection of point mutations, it is, by its nature, limited to the detection of only those single base changes which fall within a restriction sequence of a known restriction endonuclease. Moreover, the majority of the available enzymes have 4 to 6 base-pair recognition sequences, and cleave too frequently for many large-scale DNA manipulations (Eckstein and Lilley (eds.), Nucleic Acids and Molecular Biology, vol. 2, Springer-Verlag, Heidelberg [1988]). Thus, it is applicable only in a small fraction of cases, as most mutations do not fall within such sites.
A handful of rare-cutting restriction enzymes with 8 base-pair specificities have been isolated and these are widely used in genetic mapping, but these enzymes are few in number, are limited to the recognition of G+C-rich sequences, and cleave at sites that tend to be highly clustered (Barlow and Lehrach, Trends Genet., 3:167 [1987]). Recently, endonucleases encoded by group I introns have been discovered that might have greater than 12 base-pair specificity (Perlman and Butow, Science 246:1106 [1989]), but again, these are few in number.
If the change is not in a restriction enzyme recognition sequence, then allele-specific oligonucleotides (ASOs), can be designed to hybridize in proximity to the unknown nucleotide, such that a primer extension or ligation event can be used as the indicator of a match or a mis-match. Hybridization with radioactively labeled ASOs also has been applied to the detection of specific point mutations (Conner, Proc. Natl. Acad. Sci., 80:278 [1983]). The method is based on the differences in the melting temperature of short DNA fragments differing by a single nucleotide (Wallace et al., Nucl. Acids Res., 6:3543 [1979]). Similarly, hybridization with large arrays of short oligonucleotides is now used as a method for DNA sequencing (Bains and Smith, J. Theor. Biol., 135:303 [1988]) (Drmanac et al., Genomics 4:114 [1989]). To perform either method it is necessary to work under conditions in which the formation of mismatched duplexes is eliminated or reduced while perfect duplexes still remain stable. Such conditions are termed xe2x80x9chigh stringencyxe2x80x9d conditions. The stringency of hybridization conditions can be altered in a number of ways known in the art. In general, changes in conditions that enhance the formation of nucleic acid duplexes, such as increases in the concentration of salt, or reduction in the temperature of the solution, are considered to reduce the stringency of the hybridization conditions. Conversely, reduction of salt and elevation of temperature are considered to increase the stringency of the conditions. Because it is easy to change and control, variation of the temperature is commonly used to control the stringency of nucleic acid hybridization reactions.
Discrimination of hybridization based solely on the presence of a mismatch imposes a limit on probe length because effect of a single mismatch on the stability of a duplex is smaller for longer duplexes. For oligonucleotides designed to detect mutations in genomes of high complexity, such as human DNA, it has been shown that the optimal length for hybridization is between 16 and 22 nucleotides, and the temperature window within which the hybridization stringency will allow single base discrimination can be as large as 10xc2x0 C. (Wallace [1979], supra). Usually, however, it is much narrower, and for some mismatches, such as G-T, it may be as small as 1 to 2xc2x0 C. These windows may be even smaller if any other reaction conditions, such as temperature, pH, concentration of salt and the presence of destabilizing agents (e.g., urea, formamide, dimethylsulfoxide) alter the stringency. Thus, for successful detection of mutations using such high stringency hybridization methods, a tight control of all parameters affecting duplex stability is critical.
In addition to the degree of homology between the oligonucleotide probe and the target nucleic acid, efficiency of hybridization also depends on the secondary structure of the target molecule. Indeed, if the region of the target molecule that is complementary to the probe is involved in the formation of intramolecular structures with other regions of the target, this will reduce the binding efficiency of the probe. Interference with hybridization by such secondary structure is another reason why high stringency conditions are so important for sequence analysis by hybridization. High stringency conditions reduce the probability of secondary structure formation (Gamper et al., J. Mol. Biol., 197:349 [1987]). Another way to of reducing the probability of secondary structure formation is to decrease the length of target molecules, so that fewer intrastrand interactions can occur. This can be done by a number of methods, including enzymatic, chemical or thermal cleavage or degradation. Currently, it is standard practice to perform such a step in commonly used methods of sequence analysis by hybridization to fragment the target nucleic acid into short oligonucleotides (Fodor et al., Nature 364:555 [1993]).
ASOs have also been adapted to the PCR method. In this, or in any primer extension-based assay, the nucleotide to be investigated is positioned opposite the 3xe2x80x2 end of a primer oligonucleotide. If the bases are complementary, then a DNA polymerase can extend the primer with ease; if the bases are mismatched, the extension may be blocked. Blocking of PCR by this method has had some degree of success, but not all mismatches are able to block extension. In fact, a xe2x80x9cTxe2x80x9d residue on the 3xe2x80x2 end of a primer can be extended with reasonable efficiency when mis-paired with any of the non-complementary nucleotide when Taq DNA polymerase, a common PCR enzyme, is used (Kwok, et al., Nucl. Acids. Res. 18:999 [1990]). Further, if any of the enzymes having 3xe2x80x2-5xe2x80x2 exonuclease xe2x80x9cproofreadingxe2x80x9d activity (e.g., Vent DNA polymerase, New England Biolabs, Beverly Mass.) are used, the mismatch is first removed, then filled in with a matched nucleotide before further extension. This dramatically limits the scope of application of PCR in this type of direct mutation identification.
Two other methods of mutation detection rely on detecting changes in electrophoretic mobility in response to minor sequence changes. One of these methods, termed xe2x80x9cDenaturing Gradient Gel Electrophoresisxe2x80x9d (DGGE) is based on the observation that slightly different sequences will display different patterns of local melting when electrophoretically resolved on a gradient gel. In this manner, variants can be distinguished, as differences in the melting properties of homoduplexes versus heteroduplexes differing in a single nucleotide can be used to detect the presence of mutations in the target sequences because of the corresponding changes in the electrophoretic mobilities of the hetero- and homoduplexes. The fragments to be analyzed, usually PCR products, are xe2x80x9cclampedxe2x80x9d at one end by a long stretch of G-C base pairs (30-80) to allow complete denaturation of the sequence of interest without complete dissociation of the strands. The attachment of a GC xe2x80x9cclampxe2x80x9d to the DNA fragments increases the fraction of mutations that can be recognized by DGGE (Abrams et al., Genomics 7:463 [1990]). Attaching a GC clamp to one primer is critical to ensure that the amplified sequence has a low dissociation temperature (Sheffield et al., Proc. Natl. Acad. Sci., 86:232 [1989]; and Lerman and Silverstein, Meth. Enzymol., 155:482 [1987]). Modifications of the technique have been developed, using temperature gradient gels (Wartell et al., Nucl. Acids Res., 18:2699-2701 [1990]), and the method can be also applied to RNA:RNA duplexes (Smith et al., Genomics 3:217 [1988]).
Limitations on the utility of DGGE include the requirement that the denaturing conditions must be optimized for each specific nucleic acid sequence to be tested. Furthermore, the method requires specialized equipment to prepare the gels and maintain the high temperatures required during electrophoresis. The expense associated with the synthesis of the clamping tail on one oligonucleotide for each sequence to be tested is also a major consideration. In addition, long running times are required for DGGE. The long running time of DGGE was shortened in a modification of DGGE called constant denaturant gel electrophoresis (CDGE) (Borrensen et al., Proc. Natl. Acad. Sci. USA 88:8405 [1991]). CDGE requires that gels be performed under different denaturant conditions in order to reach high efficiency for the detection of unknown mutations. Both DGGE and CDGE are unsuitable for use in clinical laboratories.
A technique analogous to DGGE, termed temperature gradient gel electrophoresis (TGGE), uses a thermal gradient rather than a chemical denaturant gradient (Scholz et al., Hum. Mol. Genet., 2:2155 [1993]). TGGE requires the use of specialized equipment which can generate a temperature gradient perpendicularly oriented relative to the electrical field. TGGE can detect mutations in relatively small fragments of DNA therefore scanning of large gene segments requires the use of multiple PCR products prior to running the gel.
Another common method, called xe2x80x9cSingle-Strand Conformation Polymorphismxe2x80x9d (SSCP) was developed by Hayashi, Sekya and colleagues (reviewed by Hayashi, PCR Meth. Appl., 1:34-38, [1991]) and is based on the observation that single strands of nucleic acid can take on characteristic conformations under non-denaturing conditions, and these conformations influence electrophoretic mobility. The complementary strands assume sufficiently different structures that the two strands may be resolved from one another. Changes in the sequence of a given fragment will also change the conformation, consequently altering the mobility and allowing this to be used as an assay for sequence variations (Orita, et al., Genomics 5:874 [1989]).
The SSCP process involves denaturing a DNA segment (e.g., a PCR product) that is usually labeled on both strands, followed by slow electrophoretic separation on a non-denaturing polyacrylamide gel, so that intra-molecular interactions can form and not be disturbed during the run. This technique is extremely sensitive to variations in gel composition and temperature. A serious limitation of this method is the relative difficulty encountered in comparing data generated in different laboratories, under apparently similar conditions.
The dideoxy fingerprinting (ddF) technique is another technique developed to scan genes for the presence of unknown mutations (Liu and Sommer, PCR Methods Applic, 4:97 [1994]). The ddF technique combines components of Sanger dideoxy sequencing with SSCP. A dideoxy sequencing reaction is performed using one dideoxy terminator and then the reaction products are electrophoresed on nondenaturing polyacrylamide gels to detect alterations in mobility of the termination segments as in SSCP analysis. While ddF is an improvement over SSCP in terms of increased sensitivity, ddF requires the use of expensive dideoxynucleotides and this technique is still limited to the analysis of fragments of the size suitable for SSCP (i.e., fragments of 200-300 bases for optimal detection of mutations).
In addition to the above limitations, all of these methods are limited as to the size of the nucleic acid fragment that can be analyzed. For the direct sequencing approach, sequences of greater than 600 base pairs require cloning, with the consequent delays and expense of either deletion sub-cloning or primer walking, in order to cover the entire fragment. SSCP and DGGE have even more severe size limitations. Because of reduced sensitivity to sequence changes, these methods are not considered suitable for larger fragments. Although SSCP is reportedly able to detect 90% of single-base substitutions within a 200 base-pair fragment, the detection drops to less than 50% for 400 base pair fragments. Similarly, the sensitivity of DGGE decreases as the length of the fragment reaches 500 base-pairs. The ddF technique, as a combination of direct sequencing and SSCP, is also limited by the relatively small size of the DNA that can be screened.
Another method of detecting sequence polymorphisms based on the conformation assumed by strands of nucleic acid is the Cleavase(copyright) Fragment Length Polymorphism (CFLP(copyright)) method (Brow et al., J. Clin. Microbiol., 34:3129 [1996]; PCT International Application No. PCT/US95/14673 [WO 96/15267]; co-pending application Ser. Nos. 08/484,956 and 08/520,946). This method uses the actions of a structure specific nuclease to cleave the folded structures, thus creating a set of product fragments that can by resolved by size (e.g., by electrophoresis). This method is much less sensitive to size so that entire genes, rather than gene fragments, may be analyzed.
In many situations (e.g., in many clinical laboratories), electrophoretic separation and analysis may not be technically feasible, or may not be able to accommodate the processing of a large number of samples in a cost-effective manner. There is a clear need for a method of analyzing the characteristic conformations of nucleic acids without the need for either electrophoretic separation of conformations or fragments or for elaborate and expensive methods of visualizing gels (e.g., darkroom supplies, blotting equipment or fluorescence imagers).
In addition to the apparently fortuitous folded conformations that may be assumed by any nucleic acid segment, as noted above, the folded structures assumed by some nucleic acids are linked in a variety of ways to the function of that nucleic acid. For example, tRNA structure is critical to its proper function in protein assembly, ribosomal RNA (rRNA) structures are essential to the correct function of the ribosome, and correct folding is essential to the catalytic function of Group I self-splicing introns (See e.g., the chapters by Woese and Pace (p. 91), Noller (p. 137), and Cech (p. 239) in Gesteland and Atkins (eds.), The RNA World, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. [1993]). Folded structures in viral RNAs have been linked to infectivity (Proutski et al., J Gen Virol., 78(Pt 7):1543-1549 [1997], altered splicing (Ward, et al., Virus Genes 10:91 [1995]), translational frameshifting (Bidou et al., RNA 3:1153 [1997]), packaging (Miller, et al. J Virol., 71:7648 [1997]), and other functions. In both prokaryotes and eukaryotes, RNA structures are linked to post-transcriptional control of gene expression through mechanisms including attenuation of translation (Girelli et al., Blood 90:2084 [1997], alternative splicing (Howe and Ares, Proc. Natl. Acad. Sci. USA 94:12467 [1997]) and signaling for RNA degradation (Veyrune et al, Oncogene 11:2127 [1995]). Messenger RNA secondary structure has also been associated with localization of that RNA within cells (Serano and Cohen, Develop., 121:3809-3818 [1995]). In DNA it has been shown that cruciform structures have also been tied to control of gene expression (Hanke et al., J. Mol. Biol., 246:63 [1995]). It can be seen from these few examples that the use of folded structures as signals within organisms is not uncommon, nor is it limited to non-protein-encoding RNAs, such as rRNAs, or to non-protein-encoding regions of genomes or messenger RNAs.
Some mutations and polymorphisms associated with altered phenotype act by altering structures assumed by nucleic acids. Any of the functions and pathways cited above may be altered, e.g., decreased or increased in efficacy, by such a structural alteration. Such alterations in function may be associated with medically relevant effects, including but not limited to tumor growth or morphology (Thompson et al., Oncogene 14:1715 [1997]), drug resistance or virulence (Mangada and Igarishi, Virus Genes 14:5 [1997], Ward et al., supra) in pathogens. For example, the iron availability in blood in controlled by the protein ferritin, an iron storage protein. Ferritin levels are controlled post-transcriptionally by binding of iron-regulatory proteins to a structure (an iron-responsive element, or IRE) on 5xe2x80x2 untranslated region of the ferritin mRNA, thereby blocking translation when iron levels are low. Hereditary hyperferritinemia, an iron storage disorder linked to cataract formation, had been found in some cases to be caused by mutations in the IRE that alter or delete the structure, preventing translational regulation.
It can easily be appreciated from these few examples that ability to rapidly analyze nucleic acid structure would be a useful tool for both basic and clinical research and for diagnostics. Further, accurate identification of nucleic acid structures would facilitate the design and application of therapeutic agents targeted directly at nucleic acids, such as antisense oligonucleotides, aptamers and peptide nucleic acid agents. The present invention provides methods for designing oligonucleotides that will interact with folded nucleic acids. It is contemplated that such oligonucleotides may be used for either diagnostic (i.e., detection or analysis of structure) or therapeutic (i.e., alteration of structure function) purposes. When used to detect nucleic acid structure, it is contemplated that the resulting oligonucleotide/folded nucleic acid target complexes may be detected directly (e.g., by capture), or may be detected as the result of a further catalyzed reaction that is enabled by the complex formation, including but not limited to a ligation, a primer extension, or a nuclease cleavage reaction. It will easily be appreciated by those skilled in the art that performance of bridging oligonucleotides in these basic enzymatic reactions is indicative of their utility in assays that are based on reiterative performance of these basic reactions, including but not limited to cycle sequencing, polymerase chain reaction, ligase chain reaction, cycling probe reaction and the Invader(trademark) invasive cleavage reaction. The present invention provides methods of using the bridging oligonucleotides in each of the basic enzymatic reaction systems, and in the Invader(trademark) invasive cleavage system.
The present invention relates to methods and compositions for treating nucleic acid, and in particular, methods and compositions for detection and characterization of nucleic acid sequences and sequence changes. The present invention provides methods for examining the conformations assumed by single strands of nucleic acid, forming the basis of novel methods of detection of specific nucleic acid sequences. The present invention contemplates use of novel detection methods for, among other uses, clinical diagnostic purposes, including but not limited to the detection and identification of pathogenic organisms.
The present invention contemplates using the interactions between probe oligonucleotides and folded nucleic acid strands in methods for detection and characterization of nucleic acid sequences and sequence changes. In another embodiment, the present invention contemplates the use of structure based nucleic acid interactions in the analysis of particular structured regions of nucleic acids, as a determination of function or alteration of function. A complex formed by the specific interaction (i.e., reproducible and predictable under a given set of reaction conditions) of a probe with a target nucleic acid sequence is referred to herein as a xe2x80x9cprobe/folded target nucleic acid complex.xe2x80x9d The interactions contemplated may be a combination of standard hybridization of oligonucleotides to contiguous, co-linear complementary bases, or may include standard basepairing to non-contiguous regions of complementarity on a strand of nucleic acid to be analyzed. In this context, the term xe2x80x9cstandard base pairingxe2x80x9d refers to hydrogen bonding that occurs between complementary bases, adenosine to thymidine or uracil and guanine to cytosine to form double helical structures of the A or B form. Such standard base pairing may also be referred to as Watson-Crick base pairing. It is contemplated that the interactions between the oligonucleotides of the present invention (i.e., the probes and the targets) may include non-standard nucleic acid interactions known in the art, such as triplex structures, quadraplex aggregates, and the multibase hydrogen bonding such as is observed within nucleic acid tertiary structures, such as those found in tRNAs. It is contemplated that in one embodiment, the interactions between the oligonucleotides of the present invention may consist primarily of non-standard nucleic acid interactions. In one embodiment, the specific probe/folded target nucleic acid complex uses oligonucleotides that lack unique complementarity to each other (e.g., the shorter nucleic acid probe lacks segments that are long enough to be complementary to only a single site within the longer nucleic acid or its complement).
The present invention contemplates the use of probes that are designed to interact with non-contiguous regions of complementarity. In one embodiment, such probes are constructed by incorporating within a single oligonucleotide segments that are complementary to two or more non-contiguous regions in the target nucleic acid of interest.
In another embodiment, this mixture is present in an aqueous solution. The invention is not limited by the nature of the aqueous solution employed. The aqueous solution may contain mono- and divalent ions, non-ionic detergents, buffers, stabilizers, etc.
In one embodiment, the present invention provides a method, comprising: a) providing: i) a folded target having a deoxyribonucleic acid (DNA) sequence comprising one or more double stranded regions and one or more single stranded regions; and ii) one or more oligonucleotide probes complementary to at least a portion of the folded target; and b) mixing the folded target and the one or more probes under conditions such that the probe hybridizes to the folded target to form a probe/folded target complex. The degree of complementarity between the probes and the target nucleic acids may be complete or partial (e.g., contain at least one mismatched base pair). The method is not limited by the nature of the target DNA employed to provide the folded target DNA. In one embodiment, the target DNA comprises single-stranded DNA. In another embodiment, the target DNA comprises double-stranded DNA. Folded target DNAs may be produced from either single-stranded or double-stranded target DNAs by denaturing (e.g., heating) the DNA and then permitting the DNA to form intra-strand secondary structures. The method is not limited by the manner in which the folded target DNA is generated. The target DNA may be denatured by a variety of methods known to the art including heating, exposure to alkali, etc. and then permitted to renature under conditions that favor the formation of intra-strand duplexes (e.g., cooling, diluting the DNA solution, neutralizing the pH, etc.).
The method is also not limited by the nature of the oligonucleotide probes; these probes may comprise DNA, RNA, PNA and combinations thereof as well as comprise modified nucleotides, universal bases, adducts, etc.
In a preferred embodiment, the method further comprises detecting the presence of the probe/folded target complex. When a detection step is employed either the probe or the target DNA (or both) may comprise a label (i.e., a detectable moiety); the invention is not limited by the nature of the label employed or the location of the label (i.e., 5xe2x80x2 end, 3xe2x80x2 end, internal to the DNA sequence). A wide variety of suitable labels are known to the art and include fluorescein, tetrachlorofluorescein, hexachlorofluorescein, Cy3, Cy5, digoxigenin, radioisotopes (e.g., 32P, 35S). In another preferred embodiment, the method further comprises quantitating the amount of probe/folded target complex formed. The method is not limited by the means used for quantification; when a labeled folded target DNA is employed (e.g., fluorescein or 32P), the art knows means for quantification (e.g., determination of the amount of fluorescence or radioactivity present in the probe/folded target complex).
In a preferred embodiment, the probe in the probe/folded target complex is hybridized to a single stranded region of the folded target. In another preferred embodiment, the probe comprises an oligonucleotide having a moiety that permits its capture by a solid support. The invention is not limited by the nature of the moiety employed to permit capture. Numerous suitable moieties are known to the art, including but not limited to, biotin, avidin and streptavidin. Further, it is known in the art that many small compounds, such as fluorescein and digoxigenin may serve as haptens for specific capture by appropriate antibodies. Protein conjugates may also be used to allow specific capture by antibodies.
In a preferred embodiment the detection of the presence of the probe/folded target complex comprises exposing the probe/folded target complex to a solid support under conditions such that the probe is captured by the solid support. As discussed in further detail below, numerous suitable solid supports are known to the art (e.g., beads, particles, dipsticks, wafers, chips, membranes or flat surfaces composed of agarose, nylon, plastics such as polystyrenes, glass or silicon) and may be employed in the present methods.
In a particularly preferred embodiment, the moiety comprises a biotin moiety and the solid support comprises a surface having a compound capable of binding to the biotin moiety, the compound selected from the group consisting of avidin and streptavidin.
In another embodiment, the folded target comprises a deoxyribonucleic acid sequence having a moiety that permits its capture by a solid support; as discussed above a number of suitable moieties are known and may be employed in the present method. In yet another embodiment, the detection of the presence of the probe/folded target complex comprises exposing the probe/folded target complex to a solid support under conditions such that the folded target is captured by the solid support. In a preferred embodiment, the moiety comprises a biotin moiety and the solid support comprises a surface having a compound capable of binding to the biotin moiety, the compound selected from the group consisting of avidin and streptavidin.
In a preferred embodiment, the probe is attached to a solid support; the probe is attached to the solid support in such a manner that the probe is available for hybridization with the folded target nucleic acid. the invention is not limited by the means employed to attach the probe to the solid support. The probe may be synthesized in situ on the solid support or the probe may be attached (post-synthesis) to the solid support via a moiety present on the probe (e.g., using a biotinylated probe and solid support comprising avidin or streptavidin). In another preferred embodiment, the folded target nucleic acid is attached to a solid support; this may be accomplished for example using moiety present on the folded target (e.g., using a biotinylated target nucleic acid and solid support comprising avidin or streptavidin).
The present invention also provides a method, comprising: a) providing: i) a first folded target having a nucleic acid sequence comprising first and second portions, the first and second portions each comprising one or more double stranded regions and one or more single stranded regions; ii) a second folded target having a nucleic acid sequence comprising a first portion that is identical to the first portion of the first folded target and a second portion that differs from the second portion of the first folded target because of a variation in nucleic acid sequence relative to the first folded target, the first and second portions each comprising one or more double stranded regions and one or more single stranded regions; iii) first and second oligonucleotide probes, the first oligonucleotide probe complementary to the first portion of the first and second folded targets and the second oligonucleotide probe complementary to the second portion of the first and second folded targets; and iv) a solid support comprising first, second, third and fourth testing zones, each zone capable of capturing and immobilizing the first and second oligonucleotide probes; b) contacting the first folded target with the first oligonucleotide probe under conditions such that the first probe binds to the first folded target to form a probe/folded target complex in a first mixture; c) contacting the first folded target with the second oligonucleotide probes under conditions such that the second probe binds to the first folded target to form a probe/folded target complex in a second mixture; d) contacting the second folded target with the first oligonucleotide probe to form a third mixture; e) contacting the second folded target with the second oligonucleotide probe to form fourth mixture; and f) adding the first, second, third and fourth mixtures to the first, second, third and fourth testing zones of the solid support, respectively, under conditions such that the probes are captured and immobilized. The degree of complementarity between the probes and the target nucleic acids may be complete or partial (e.g., contain at least one mismatched base pair).
In a preferred embodiment, the first probe in step d) does not substantially hybridize to the second folded target; that is while it is not required that absolutely no formation of a first probe/second folded target complex occurs, very little of this complex is formed. In another preferred embodiment, the hybridization of the first probe in step d) to the second folded target is reduced relative to the hybridization of the first probe in step c) to the first folded target.
The method is not limited by the nature of the first and second targets. The first and second targets may comprise double- or single-stranded DNA or RNA. The method is also not limited by the nature of the oligonucleotide probes; these probes may comprise DNA, RNA, PNA and combinations thereof as well as comprise modified nucleotides, universal bases, adducts, etc. In a preferred embodiment, the first and second oligonucleotide probes comprise DNA.
The present invention further provides a method, comprising: a) providing: i) a first folded target having a nucleic acid sequence comprising first and second portions, the first and second portions each comprising one or more double stranded regions and one or more single stranded regions; ii) a second folded target having a nucleic acid sequence comprising a first portion that is identical to the first portion of the first folded target and a second portion that differs from the second portion of the first folded target because of a variation in nucleic acid sequence relative to the first folded target, the first and second portions each comprising one or more double stranded regions and one or more single stranded regions; iii) a solid support comprising first and second testing zones, each of the zones comprising immobilized first and second oligonucleotide probes, the first oligonucleotide probe complementary to the first portion of the first and second folded targets and second oligonucleotide probe complementary to the second portion of the first and second folded targets; and b) contacting the first and second folded targets with the solid support under conditions such that the first and second probes hybridize to the first folded target to form a probe/folded target complex. The invention is not limited by the nature of the first and second folded targets. The first and second targets may be derived from double- or single-stranded DNA or RNA. The probes may be completely or partially complementary to the target nucleic acids. The method is also not limited by the nature of the oligonucleotide probes; these probes may comprise DNA, RNA, PNA and combinations thereof as well as comprise modified nucleotides, universal bases, adducts, etc. In a preferred embodiment, the first and second oligonucleotide probes comprise DNA. The invention is not limited by the nature of the solid support employed as discussed above.
In a preferred embodiment, the contacting of step b) comprises adding the first folded target to the first testing zone and adding the second folded target to the second testing zone. In another preferred embodiment, the first and second probes are immobilized in separate portions of the testing zones.
In a preferred embodiment, the first probe in the second testing zone does not substantially hybridize to the second folded target; that is while it is not required that absolutely no formation of a first probe/second folded target complex occurs, very little of this complex is formed. In another preferred embodiment, the first probe in the second testing zone hybridizes to the second folded target with a reduced efficiency compared to the hybridization of the first probe in first testing zone to the first folded target.
In one embodiment, the first and second folded targets comprise DNA. In another embodiment, the first and second folded targets comprise RNA. The present invention also provides a method for treating nucleic acid, comprising: a) providing: i) a nucleic acid target and ii) one or more oligonucleotide probes; b) treating the nucleic acid target and the probes under conditions such that the target forms one or more folded structures and interacts with one or more probes; and c) analyzing the complexes formed between the probes and the target. In a preferred embodiment, the method further comprises providing a solid support for the capture of the target/probe complexes. Such capture may occur after the formation of the structures, or either the probe or the target my be bound to the support before complex formation.
The method is not limited by the nature of the nucleic acid target employed. In one embodiment, the nucleic acid of step (a) is substantially single-stranded. In another embodiment, the nucleic acid is RNA or DNA. It is contemplated that the nucleic acid target comprise a nucleotide analog, including but not limited to the group comprising 7-deaza-dATP, 7-deaza-dGTP and dUTP. The nucleic acid target may be double stranded. When double-stranded nucleic acid targets are employed, the treating of step (b) comprises: i) rendering the double-stranded nucleic acid substantially single-stranded; and ii) exposing the single-stranded nucleic acid to conditions such that the single-stranded nucleic acid has secondary structure. The invention is not limited by the method employed to render the double-stranded nucleic acid substantially single-stranded; a variety of means known to the art may be employed. A preferred means for rendering double stranded nucleic acid substantially single-stranded is by the use of increased temperature.
In a preferred embodiment, the method further comprises the step of detecting the one or more target/probe complexes. The invention is not limited by the methods used for the detection of the complex(es).
It is contemplated that the methods of the present invention be used for the detection and identification of microorganisms. It is contemplated that the microorganism(s) of the present invention be selected from a variety of microorganisms; it is not intended that the present invention be limited to any particular type of microorganism. Rather, it is intended that the present invention will be used with organisms including, but not limited to, bacteria, fungi, protozoa, ciliates, and viruses. It is not intended that the microorganisms be limited to a particular genus, species, strain, or serotype. Indeed, it is contemplated that the bacteria be selected from the group comprising, but not limited to members of the genera Campylobacter, Escherichia, Mycobacterium, Salmonella, Shigella, and Staphylococcus. In one preferred embodiment, the microorganism(s) comprise strains of multi-drug resistant Mycobacterium tuberculosis. It is also contemplated that the present invention be used with viruses, including but not limited to hepatitis C virus, human immunodeficiency virus, simian immunodeficiency virus, and influenza virus (e.g., influenza type A)
Another embodiment of the present invention contemplates a method for detecting and identifying strains of microorganisms, comprising the steps of extracting nucleic acid from a sample suspected of containing one or more microorganisms; and contacting the extracted nucleic acid with one or more oligonucleotide probes under conditions such that the extracted nucleic acid forms one or more secondary structures and interacts with one or more probes. In one embodiment, the method further comprises the step of capturing the complexes to a solid support. In yet another embodiment, the method further comprises the step of detecting the captured complexes. In one preferred embodiment, the present invention further comprises comparing the detected from the extracted nucleic acid isolated from the sample with separated complexes derived from one or more reference microorganisms. In such a case the sequence of the nucleic acids from one or more reference microorganisms may be related but different (e.g., a wild type control for a mutant sequence or a known or previously characterized mutant sequence).
In an alternative preferred embodiment, the present invention further comprises the step of isolating a polymorphic locus from the extracted nucleic acid after the extraction step, so as to generate a nucleic acid target, wherein the target is contacted with one or more probe oligonucleotides. In one embodiment, the isolation of a polymorphic locus is accomplished by polymerase chain reaction amplification. In an alternate embodiment, the polymerase chain reaction is conducted in the presence of a nucleotide analog, including but not limited to the group comprising 7-deaza-dATP, 7-deaza-dGTP and dUTP. It is contemplated that the polymerase chain reaction amplification will employ oligonucleotide primers matching or complementary to consensus gene sequences derived from the polymorphic locus. In one embodiment, the polymorphic locus comprises a ribosomal RNA gene. In a particularly preferred embodiment, the ribosomal RNA gene is a 16S ribosomal RNA gene.
The present invention also contemplates a process for creating a record reference library of genetic fingerprints characteristic (i.e., diagnostic) of one or more alleles of the various microorganisms, comprising the steps of providing a nucleic acid target derived from microbial gene sequences; comprising the steps of extracting nucleic acid from a sample suspected of containing one or more microorganisms; and contacting the extracted nucleic acid with one or more oligonucleotide probes under conditions such that the extracted nucleic acid forms one or more secondary structures and interacts with one or more probes; detecting the captured complexes; and maintaining a testable record reference of the captured complexes.
By the term xe2x80x9cgenetic fingerprintxe2x80x9d it is meant that changes in the sequence of the nucleic acid (e.g., a deletion, insertion or a single point substitution) alter both the sequences detectable by standard base pairing, and alter the structures formed, thus changing the profile of interactions between the target and the probe oligonucleotides (e.g., altering the identity of the probes with which interaction occurs and/or altering the site/s or strength of the interaction). The measure of the identity of the probes bound and the strength of the interactions constitutes an informative profile that can serve as a xe2x80x9cfingerprintxe2x80x9d of the nucleic acid, reflecting the sequence and allowing rapid detection and identification of variants.
The methods of the present invention allow for simultaneous analysis of both strands (e.g., the sense and antisense strands) and are ideal for high-level multiplexing. The products produced are amenable to qualitative, quantitative and positional analysis. The present methods may be automated and may be practiced in solution or in the solid phase (e.g., on a solid support). The present methods are powerful in that they allow for analysis of longer fragments of nucleic acid than current methodologies.
The present invention further provides methods for determination of structure formation in nucleic acid targets, comprising the steps of: a) providing: i) a folded target having a deoxyribonucleic acid sequence comprising one or more double stranded regions, and one or more single stranded regions, and further comprising two or more non-contiguous portions, and one or more intervening regions; and ii) one or more bridging oligonucleotide probes complementary to two or more non-contiguous portions of the folded target; and b) mixing the folded target and one or more bridging oligonucleotide probes under conditions such that the bridging oligonucleotide probes hybridize to the folded target to form a probe/folded target complex.
In preferred embodiments, the one or more intervening regions of the folded targets comprise at least five nucleotides. In yet other embodiments, either of the targets and/or either of the bridging oligonucleotides contain intervening regions comprised of non-nucleotide spacers of any length. In a preferred embodiment, the first and second oligonucleotide probes comprise DNA. In alternative embodiments, the method further comprises detecting the presence of the probe/folded target complex. In yet other embodiments, the method further comprises quantitating the amount of probe/folded target complex formed. In yet other embodiments of the method, the bridging oligonucleotide probe in the probe/folded target complex is hybridized to at least one single stranded region of the folded target.
The method is not limited by the nature of the target DNA employed to provide the folded target DNA, nor is the method limited by the manner in which the folded target DNA is generated. The method is also not limited by the nature of the bridging oligonucleotide probes; these probes may comprise DNA, RNA, PNA and combinations thereof as well as comprise modified nucleotides, universal bases, adducts, etc.
In a preferred embodiment, the method further comprises detecting the presence of the probe/folded target complex. When a detection step is employed either the bridging oligonucleotide probe or the target DNA (or both) may comprise a label (i.e., a detectable moiety); the invention is not limited by the nature of the label employed or the location of the label (i.e., 5xe2x80x2 end, 3xe2x80x2 end, internal to the DNA sequence). A wide variety of suitable labels are known to the art and include fluorescein, tetrachlorofluorescein, hexachlorofluorescein, Cy3, Cy5, digoxigenin, radioisotopes (e.g., 32P, 35S). In another preferred embodiment, the method further comprises quantitating the amount of probe/folded target complex formed. The method is not limited by the means used for quantification; when a labeled folded target DNA is employed (e.g., fluorescein or 32P), the art knows means for quantification (e.g., determination of the amount of fluorescence or radioactivity present in the probe/folded target complex).
Detection of the probe/folded target complex may also involve a catalyzed reaction on the probe that can only occur upon binding. It is contemplated that such catalyzed reaction may be mediated by an enzyme. By way of example, but not by way of limitation, the bound bridging oligonucleotide probe may be extended by a DNA polymerase, joined to another nucleic acid by the action of a ligase, or cleaved by a structure-specific nuclease. It is further contemplated that the catalytic action may be chemical, rather then enzymatic. For example, the cleavage of nucleic acid by compounds such as phenanthroline-Cu is specific for duplexed structures. It is contemplated that any chemical that can act upon nucleic acid in a manner that is responsive to the strandedness or other structural feature of the complex of the target may be used in the detection of the probe/folded target complex.
It is contemplated that any catalyzed reaction that is specifically operative on a duplex formed between a target nucleic acid and a substantially complementary probe may be configured to perform on the bridging probe/folded target complex.
In another embodiment the bound probe may participate in a reaction requiring a one or more additional nucleic acids, such as ligation reaction a polymerase chain reaction, a 5xe2x80x2 nuclease reaction, (Lyamichev et al., Science 260: 778 [1993]; U.S. Pat. No. 5,422,253, herein incorporated by reference), or an Invader(trademark) invasive cleavage reaction (PCT International Application No. PCT/US97/01072 [WO 97/27214]; co-pending application Ser. Nos. 08/599,491, 08/682,853, 08/756,386, 08/759,038, and 08/823,516, all of which are herein incorporated by reference). In one embodiment, the additional nucleic acid includes another hybridized probe. In another embodiment, the additional nucleic acid included the target. In a preferred embodiment, the additional nucleic acid includes a bridging oligonucleotide probe complementary to two or more non-contiguous portions of the folded target.
It is contemplated that a nucleic acid on which the catalyzed reaction acts may be labeled. Thus detection of the complex on which the catalyzed reaction has acted may comprise detection of a labeled product or products of that reaction. The invention is not limited by the nature of the label used, including, but not limited to, labels which comprise a dye or a radionuclide (e.g., 32P), fluorescein moiety, a biotin moiety, luminogenic, fluorogenic, phosphorescent, or fluorophores in combination with moieties that can suppress emission by fluorescence resonance energy transfer (FRET). Numerous methods are available for the detection of nucleic acids containing any of the above-listed labels. For example, biotin-labeled oligonucleotide(s) may be detected using non-isotopic detection methods which employ streptavidin-alkaline phosphatase conjugates. Fluorescein-labeled oligonucleotide(s) may be detected using a fluorescein-imager. The oligonucleotides may be labeled with different labels. The different labels may be present on the probe before the catalytic reaction. In this embodiment the release of the labels from attachment to the same complex (e.g., by FRET analysis), may be used to detect formation of the probe/folded target complex. Alternatively, one or more of the labels may be added to the complex as a result of the catalytic reaction (e.g., by ligation to a labeled nucleic acid or by polymerization using labeled nucleoside triphosphates).
It is also contemplated that labeled oligonucleotides (reacted or unreacted) may be separated by means other than electrophoresis. For example, biotin-labeled oligonucleotides may be separated from nucleic acid present in the reaction mixture using para-magnetic or magnetic beads, or particles which are coated with avidin (or streptavidin). In this manner, the biotinylated oligonucleotide/avidin-magnetic bead complex can be physically separated from the other components in the mixture by exposing the complexes to a magnetic field. Additionally, the signal from the reacted oligonucleotides may be resolved from that of the unreacted oligonucleotides without physical separation. For example, a change in size as may be caused by binding to another oligonucleotide, or by cleavage, ligation or polymerase extension of at least one nucleic acid in the complex, will change the rate of rotation in solution, allowing of fluorescently labeled complexes or product molecules to be detected by fluorescence polarization analysis. However, it is not intended that the means of analysis be limited to those methods of cited above. Those skilled in the art of nucleic acid analysis will appreciate that there are numerous additional methods for the analysis of both of labeled and unlabeled nucleic acids that are readily adaptable for the detection of the probe/folded target complexes of the present invention.
In another preferred embodiment, the bridging oligonucleotide probe comprises a bridging oligonucleotide having a moiety that permits its capture by a solid support. The invention is not limited by the nature of the moiety employed to permit capture. Numerous suitable moieties are known to the art, including but not limited to, biotin, avidin and streptavidin. Further, it is known in the art that many small compounds, such as fluorescein and digoxigenin may serve as haptens for specific capture by appropriate antibodies. Protein conjugates may also be used to allow specific capture by antibodies.
In a preferred embodiment the detection of the presence of the probe/folded target complex comprises exposing the probe/folded target complex to a solid support under conditions such that the bridging oligonucleotide probe is captured by the solid support. As discussed in further detail below, numerous suitable solid supports are known to the art (e.g., beads, particles, dipsticks, wafers, chips, membranes or flat surfaces composed of agarose, nylon, plastics such as polystyrenes, glass or silicon) and may be employed in the present methods.
In a particularly preferred embodiment, the moiety comprises a biotin moiety and the solid support comprises a surface having a compound capable of binding to the biotin moiety, the compound selected from the group consisting of avidin and streptavidin.
In another embodiment, the folded target comprises a deoxyribonucleic acid sequence having a moiety that permits its capture by a solid support; as discussed above a number of suitable moieties are known and may be employed in the present method. In yet another embodiment, the detection of the presence of the probe/folded target complex comprises exposing the probe/folded target complex to a solid support under conditions such that the folded target is captured by the solid support. In a preferred embodiment, the moiety comprises a biotin moiety and the solid support comprises a surface having a compound capable of binding to the biotin moiety, the compound selected from the group consisting of avidin and streptavidin.
In a preferred embodiment, the bridging oligonucleotide probe is attached to a solid support; the probe is attached to the solid support in such a manner that the bridging oligonucleotide probe is available for hybridization with the folded target nucleic acid. The invention is not limited by the means employed to attach the bridging oligonucleotide probe to the solid support. The bridging oligonucleotide probe may be synthesized in situ on the solid support or the probe may be attached (post-synthesis) to the solid support via a moiety present on the bridging oligonucleotide probe (e.g., using a biotinylated probe and solid support comprising avidin or streptavidin). In another preferred embodiment, the folded target nucleic acid is attached to a solid support; this may be accomplished for example using a moiety present on the folded target (e.g., using a biotinylated target nucleic acid and solid support comprising avidin or streptavidin).
The present invention also provides methods for analyzing the structure of nucleic acid targets, comprising: a) providing: i) a first folded target having a nucleic acid sequence comprising first and second portions, the first and second portions each comprising one or more double stranded regions and one or more single stranded regions; ii) a second folded target having a nucleic acid sequence comprising a first portion that is identical to the first portion of the first folded target and a second portion that differs from the second portion of the first folded target because of a variation in nucleic acid sequence relative to the first folded target, the first and second portions each comprising one or more double stranded regions and one or more single stranded regions; iii) first and second bridging oligonucleotides, wherein the first bridging oligonucleotide is complementary to the first portion of the first and second folded targets and the second bridging oligonucleotide is complementary to the second portion of the first and second folded targets; and iv) a solid support comprising first, second, third and fourth testing zones, each zone capable of capturing and immobilizing the first and second bridging oligonucleotides; b) contacting the first folded target with the first bridging oligonucleotide under conditions such that the first bridging oligonucleotide binds to the first folded target to form a probe/folded target complex in a first mixture; c) contacting the first folded target with the second bridging oligonucleotide under conditions such that the second bridging oligonucleotide binds to the first folded target to form a probe/folded target complex in a second mixture; d) contacting the second folded target with the first bridging oligonucleotide to form a third mixture; e) contacting the second folded target with the second bridging oligonucleotide to form fourth mixture; and f) adding the first, second, third and fourth mixtures to the first, second, third and fourth testing zones of the solid support, respectively, under conditions such that the first and second bridging oligonucleotides are captured and immobilized.
The method is not limited by the nature of the first and second targets. The first and/or second target may comprise one or more non-contiguous regions, as well as one or more intervening regions. In preferred embodiments, the intervening regions comprise at least five nucleotides. The method is also not limited by the nature of the bridging oligonucleotide probes; these bridging oligonucleotide probes may comprise DNA, RNA, PNA and combinations thereof as well as comprise modified nucleotides, universal bases, adducts, etc. In some embodiments, the first and/or second bridging oligonucleotide probes comprise one or more intervening regions. In alternative embodiments, the intervening region of the bridging oligonucleotide probes comprises at least two nucleotides. In yet other embodiments, either of the targets and/or either of the bridging oligonucleotides contain intervening regions comprised of non-nucleotide spacers of any length. In a preferred embodiment, the first and second oligonucleotide probes comprise DNA. In a preferred embodiment, the first and second bridging oligonucleotide probes comprise DNA.
In alternative embodiments, the first bridging oligonucleotide in step d) does not substantially hybridize to the second folded target. In yet another embodiment, the hybridization of the first bridging oligonucleotide in step d) to the second folded target is reduced relative to the hybridization of the first bridging oligonucleotide in step c) to the first folded target. In further embodiments, the first and second targets comprise DNA, and/or the first and second bridging oligonucleotides comprise DNA.
The present invention also provides methods for analyzing folded nucleic acid targets, comprising: a) providing: i) a first folded target having a nucleic acid sequence comprising first and second portions, wherein the first and second portions each comprise one or more double stranded regions and one or more single stranded regions; ii) a second folded target having a nucleic acid sequence comprising a first portion that is identical to the first portion of the first folded target, and a second portion that differs from the second portion of the first folded target because of a variation in nucleic acid sequence relative to the first folded target, the first and second portions each comprising one or more double stranded regions and one or more single stranded regions; iii) a solid support comprising first and second testing zones, each of the zones comprising immobilized first and second bridging oligonucleotides, the first bridging oligonucleotide being complementary to the first portion of the first and second folded targets and second bridging oligonucleotide being complementary to the second portion of the first and second folded targets; and b) contacting the first and second folded targets with the solid support under conditions such that the first and second bridging oligonucleotides hybridize to the first folded target to form a probe/folded target complex.
In some embodiments, the contacting of step b) comprises adding the first folded target to the first testing zone and adding the second folded target to the second testing zone. In alternative embodiments, the first and second bridging oligonucleotides are immobilized in separate portions of the testing zones. In yet other embodiments, the first bridging oligonucleotide in the second testing zone does not substantially hybridize to the second folded target. In further embodiments, the first bridging oligonucleotide in the second testing zone hybridizes to the second folded target with a reduced efficiency compared to the hybridization of the first bridging oligonucleotide in first testing zone to the first folded target. The method is not limited by the nature of, nor the method of generating the first and second folded targets. The method is also not limited by the nature of, or the method of generating the oligonucleotide probes; these probes may comprise DNA, RNA, PNA and combinations thereof as well as comprise modified nucleotides, universal bases, adducts, etc. In some embodiments, the first and/or second folded target comprises one or more intervening region comprised of at least five nucleotides. In yet other embodiments, the first and/or second bridging oligonucleotide probe comprises one or more intervening regions comprised of at least two nucleotides. In yet other embodiments, either of the targets and/or either of the bridging oligonucleotides contain intervening regions comprised of non-nucleotide spacers of any length. In a preferred embodiment, the first and second oligonucleotide probes comprise DNA. The invention is not limited by the nature of the solid support employed as discussed above. In some preferred embodiments of the method, the first and second folded targets comprise DNA. In alternative embodiments, the first and second folded targets comprise RNA. In yet other embodiments, the first and second bridging oligonucleotides comprise DNA.
The present invention provides methods for detection of structured nucleic acid targets, comprising the steps of: a) providing: i) a folded target having a nucleic acid sequence comprising one or more double stranded regions, and one or more single stranded regions, and further comprising two or more non-contiguous portions, and one or more intervening regions; ii) at least one bridging oligonucleotide probe capable of binding to two or more non-contiguous portions of said folded target; and iii) a reactant; b) mixing said folded target and said probe under conditions such that said probe hybridizes to said folded target to form a probe/folded target complex; and c) treating said probe/folded target complex with said reactant to produce at least one modified probe. In one embodiment the method further provides for the detection of said modified probe.
The present invention further provides a method, comprising: a) providing target nucleic acid comprising first and second non-contiguous single-stranded regions separated by an intervening region comprising a double-stranded portion; a bridging oligonucleotide capable of binding to said first and second non-contiguous single-stranded regions; and a reactant selected from the group consisting of polymerases and ligases; and mixing said target nucleic acid, said bridging oligonucleotide and said reactant under conditions such that said bridging oligonucleotide is modified to produce a modified oligonucleotide.
In some embodiments of the methods, the reactant is a polymerase, while in yet other embodiments, the modified oligonucleotide comprises an extended oligonucleotide. In still other embodiments, the reactant is a polymerase and the modified oligonucleotide comprises extended oligonucleotide. In yet other embodiments, the reactant is a ligase, while in yet other embodiments, the modified oligonucleotide comprises a ligated oligonucleotide. In still other embodiments, the reactant is a ligase and the modified oligonucleotide comprises a ligated oligonucleotide.
In yet other embodiments of the method, the bridging oligonucleotide is capable of binding to fewer than ten nucleotides of each of said first and second non-contiguous single-stranded regions. In still other embodiments, the bridging oligonucleotide is capable of binding to eight or fewer nucleotides of each of said first and second non-contiguous single-stranded regions.
In further embodiments of the method the target nucleic acid is DNA, while in some preferred embodiments, the DNA is viral DNA. In yet other preferred embodiments, the virus is selected from the group consisting of Parvoviridae, Papovaviridae, Adenoviridae, Hepadnaviridae, Herpesviridae, Iridoviridae, and Poxviridae. For example, it is intended that the present invention encompass methods for the detection of any DNA-containing virus, including, but not limited to parvoviruses, dependoviruses, papillomaviruses, polyomaviruses, mastadenoviruses, aviadenoviruses, hepadnaviruses, simplexviruses [such as herpes simplex virus 1 and 2], varicelloviruses, cytomegaloviruses, muromegaloviruses, lymphocryptoviruses, thetalymphocryptoviruses, rhadinoviruses, iridoviruses, ranaviruses, pisciniviruses, orthopoxviruses, parapoxviruses, avipoxviruses, capripoxviruses, leporipoxviruses, suipoxviruses, yatapoxviruses, and mulluscipoxvirus). Thus, it is not intended that the present invention be limited to any DNA virus family.
In further embodiments of the method the target nucleic acid is RNA, while in some preferred embodiments, the RNA is viral RNA. In yet other preferred embodiments, the virus is selected from the group consisting of Picornaviridae, Caliciviridae, Reoviridae, Togaviridae, Flaviviridae, Orthomyxoviridae, Paramyxoviridae, Arenaviridae, Rhabdoviridae, Coronaviridae, Bunyaviridae, and Retroviridae. For example, it is intended that the present invention encompass methods for the detection of RNA-containing virus, including, but not limited to enteroviruses (e.g., polioviruses, Coxsackieviruses, echoviruses, enteroviruses, hepatitis A virus, encephalomyocarditis virus, mengovirus, rhinoviruses, and aphthoviruses), caliciviruses, reoviruses, orbiviruses, rotaviruses, birnaviruses, alphaviruses, rubiviruses, pestiviruses, flaviviruses (e.g., hepatitis C virus, yellow fever viruses, dengue, Japanese, Murray Valley, and St. Louis encephalitis viruses, West Nile fever virus, Kyanasur Forest disease virus, Omsk hemorrhagic fever virus, European and Far Eastern tick-borne encephalitis viruses, and louping ill virus), influenzaviruses (e.g, types A, B, and C), paramyxoviruses, morbilliviruses, pneumoviruses, veisculoviruses, lyssaviruses, filoviruses, coronaviruses, bunyaviruses, phleboviruses, nairoviruses, uukuviruses, hantaviruses, sarcoma and leukemia viruses, oncoviruses, HTLV, spumaviruses, lentiviruses, and arenaviruses).
The present invention also provides a method, comprising: a) providing target nucleic acid comprising first and second non-contiguous single-stranded regions separated by an intervening region comprising a double-stranded region; a bridging oligonucleotide capable of binding to said first and second non-contiguous single-stranded regions; a second oligonucleotide capable of binding to a portion of said first non-contiguous single-stranded region; and a cleavage means; b) mixing said target nucleic acid, said bridging oligonucleotide, said second oligonucleotide, and said cleavage means under conditions such that either said second oligonucleotide or said bridging oligonucleotide is cleaved.
In some preferred embodiments, the cleavage means comprises a nuclease. In other preferred embodiments, the cleavage means comprises a thermostable 5xe2x80x2 nuclease. In still other preferred embodiments, the thermostable 5xe2x80x2 nuclease comprises an altered polymerase derived from a native polymerases of Thermus species.
In other embodiments of the method, the conditions of mixing allow for hybridization of said bridging oligonucleotide and said second oligonucleotide to said target nucleic acid so as to define a region of overlap of said oligonucleotides. In some embodiments, the region of overlap comprises one base, while in other embodiments, the region of overlap comprises more than one base.
In further embodiments of the method the target nucleic acid is DNA, while in some preferred embodiments, the DNA is viral DNA. In yet other preferred embodiments, the virus is selected from the group consisting of Parvoviridae, Papovaviridae, Adenoviridae, Hepadnaviridae, Herpesviridae, Iridoviridae, and Poxviridae. For example, it is intended that the present invention encompass methods for the detection of any DNA-containing virus, including, but not limited to parvoviruses, dependoviruses, papillomaviruses, polyomaviruses, mastadenoviruses, aviadenoviruses, hepadnaviruses, simplexviruses [such as herpes simplex virus 1 and 2], varicelloviruses, cytomegaloviruses, muromegaloviruses, lymphocryptoviruses, thetalymphocryptoviruses, rhadinoviruses, iridoviruses, ranaviruses, pisciniviruses, orthopoxviruses, parapoxviruses, avipoxviruses, capripoxviruses, leporipoxviruses, suipoxviruses, yatapoxviruses, and mulluscipoxvirus). Thus, it is not intended that the present invention be limited to any DNA virus family.
In further embodiments of the method the target nucleic acid is RNA, while in some preferred embodiments, the RNA is viral RNA. In yet other preferred embodiments, the virus is selected from the group consisting of Picornaviridae, Caliciviridae, Reoviridae, Togaviridae, Flaviviridae, Orthomyxoviridae, Paramyxoviridae, Arenaviridae, Rhabdoviridae, Coronaviridae, Bunyaviridae, and Retroviridae. For example, it is intended that the present invention encompass methods for the detection of RNA-containing virus, including, but not limited to enteroviruses (e.g., polioviruses, Coxsackieviruses, echoviruses, enteroviruses, hepatitis A virus, encephalomyocarditis virus, mengovirus, rhinoviruses, and aphthoviruses), caliciviruses, reoviruses, orbiviruses, rotaviruses, bimaviruses, alphaviruses, rubiviruses, pestiviruses, flaviviruses ([e.g., hepatitis C virus, yellow fever viruses, dengue, Japanese, Murray Valley, and St. Louis encephalitis viruses, West Nile fever virus, Kyanasur Forest disease virus, Omsk hemorrhagic fever virus, European and Far Eastern tick-borne encephalitis viruses, and louping ill virus], influenzaviruses (e.g, types A, B, and C), paramyxoviruses, morbilliviruses, pneumoviruses, veisculoviruses, lyssaviruses, filoviruses, coronaviruses, bunyaviruses, phleboviruses, nairoviruses, uukuviruses, hantaviruses, sarcoma and leukemia viruses, oncoviruses, HTLV, spumaviruses, lentiviruses, and arenaviruses).
The present invention also provides a method, comprising: a) providing target nucleic acid comprising first and second non-contiguous single-stranded regions separated by an intervening region, said intervening region comprising a first double-stranded portion and a second double-stranded portion separated by a connecting single-stranded portion; and a bridging oligonucleotide capable of binding to said first and second non-contiguous single-stranded regions; and b) mixing said target nucleic acid and said bridging oligonucleotide under conditions such that said bridging oligonucleotide hybridizes to said target to form an oligonucleotide/target complex.
In further embodiments of the method the target nucleic acid is DNA, while in some preferred embodiments, the DNA is viral DNA. In yet other preferred embodiments, the virus is selected from the group consisting of Parvoviridae, Papovaviridae, Adenoviridae, Hepadnaviridae, Herpesviridae, Iridoviridae, and Poxviridae. For example, it is intended that the present invention encompass methods for the detection of any DNA-containing virus, including, but not limited to parvoviruses, dependoviruses, papillomaviruses, polyomaviruses, mastadenoviruses, aviadenoviruses, hepadnaviruses, simplexviruses [such as herpes simplex virus 1 and 2], varicelloviruses, cytomegaloviruses, muromegaloviruses, lymphocryptoviruses, thetalymphocryptoviruses, rhadinoviruses, iridoviruses, ranaviruses, pisciniviruses, orthopoxviruses, parapoxviruses, avipoxviruses, capripoxviruses, leporipoxviruses, suipoxviruses, yatapoxviruses, and mulluscipoxvirus). Thus, it is not intended that the present invention be limited to any DNA virus family.
In further embodiments of the method the target nucleic acid is RNA, while in some preferred embodiments, the RNA is viral RNA. In yet other preferred embodiments, the virus is selected from the group consisting of Picornaviridae, Caliciviridae, Reoviridae, Togaviridae, Flaviviridae, Orthomyxoviridae, Paramyxoviridae, Arenaviridae, Rhabdoviridae, Coronaviridae, Bunyaviridae, and Retroviridae. For example, it is intended that the present invention encompass methods for the detection of RNA-containing virus, including, but not limited to enteroviruses (e.g., polioviruses, Coxsackieviruses, echoviruses, enteroviruses, hepatitis A virus, encephalomyocarditis virus, mengovirus, rhinoviruses, and aphthoviruses), caliciviruses, reoviruses, orbiviruses, rotaviruses, birnaviruses, alphaviruses, rubiviruses, pestiviruses, flaviviruses (e.g., hepatitis C virus, yellow fever viruses, dengue, Japanese, Murray Valley, and St. Louis encephalitis viruses, West Nile fever virus, Kyanasur Forest disease virus, Omsk hemorrhagic fever virus, European and Far Eastern tick-borne encephalitis viruses, and louping ill virus), influenzaviruses (e.g, types A, B, and C), paramyxoviruses, morbilliviruses, pneumoviruses, veisculoviruses, lyssaviruses, filoviruses, coronaviruses, bunyaviruses, phleboviruses, nairoviruses, uukuviruses, hantaviruses, sarcoma and leukemia viruses, oncoviruses, HTLV, spumaviruses, lentiviruses, and arenaviruses).